1. Field of the Invention
This invention relates to apparatus for applying refractory material to the interior surfaces of vessels adapted to contain molten metal.
2. Description of the Prior Art
In the metallurgical art, it is common practice to patch or supplement the refractory linings of vessels adapted to contain molten metal while such vessels remain in service. Typical of the vessels to which such practice is applied are open-top hot metal ladles. In the steel industry, for example, large refractory-lined vessels are used to receive a heat of steel from the refining furnace and move the molten steel into position for pouring it into a continuous casting machine or into conventional ingot molds. During these operations, wear on the refractory lining of the ladle tends to be uneven; the service life of that lining may be prolonged by performing selective patching or lining supplementation without removing the ladle completely from service for a lining replacement.
Workers in the art have recognized the desirability of providing mechanical means for accomplishing these patching procedures; the principal advantage is timesaving, but awkward manual operations performed in a high temperature setting also may be eliminated by mechanical apparatus designed to propel a pasty refractory material against the refractory walls of a vessel. Haus U.S. Pat. No. 3,797,745 represents an early attempt at providing a mechanical refractory applicator. That patent discloses an arrangement of two concentric tubes suspended from above the ladle mouth and having rotatable discharge nozzles connected to the conduits at their lower ends for mixing dry refractory material and water passed through the outer and inner conduits, respectively, and applying the mixture to the interior walls of the ladle. The apparatus of U.S. Pat. No. 3,797,745 requires, however, that the lower portions of both conduits rotate relative to their upper portions. This rotation is achieved by the use of a rotary coupling immediate the ends of each conduit. The fact that both conduits rotate narrowly restricts any tolerance for longitudinal misalignment in the structure and this limitation is manifested in higher manufacturing and assembly costs as well as in frequent maintenance during operation.
A further problem associated with the apparatus of U.S. Pat. No. 3,797,745 is that the refractory material is conveyed through the annular passageway between the inner and outer conduits while water is conveyed through the inner conduit. In practice, the abrasion of the granular refractory material on the outer wall of the water-carrying inner conduit results in frequent breakthroughs in those outer walls and consequent shutdowns to replace the inner conduit. Further, the operation of the apparatus is dependent upon the relatively equal division of flow of refractory material between the two discharge nozzles at the bottom of the apparatus. Flow of refractory in the annular passageway between the conduits is not conductive to achieving such equal division.
Another arrangement for applying granular refractory material to the linings of ladles and the like is shown in U.S. Pat. No. 4,099,708. This arrangement is directed largely to the selective application of refractory on lining walls. As in U.S. Pat. No. 3,797,745, the apparatus includes two concentric conduits which rotate together; however, the conveyance of materials is reversed in that refractory material flows in the inner conduit and water flows in the annulus between the conduits. Nevertheless, the same structural and operating problems associated with two rotating concentric conduits that are discussed above with respect to U.S. Pat. No. 3,797,745 are present in the '708 apparatus.
A more recent attempt to devise a refractory applicator is shown in Haus U.S. Pat. No. 4,167,246. That apparatus reveals an abandonment of the two concentric conduits concept in favor of a single rotating conduit for conveying refractory material with the water being supplied externally of the applicator through flexible hoses. As a result, the '246 device is incapable of continuous rotation.